1. Field of the Invention
The present invention relates to methods and systems of recognizing handwritten characters.
2. Description of the Background Art
In recent years a pen rather than a keyboard has been used to input characters in portable information equipment and the like. For example, for a tablet with display and input devices integrated therein that is mounted, e.g., in a PDC, recognition rate of handwritten characters input thereto is an important factor in evaluating the value thereof as a product. Methods of such character recognition include comparing stroke coordinates of a handwritten character with a dictionary database, comparing the writing direction of a handwritten character as well as its originating order with a dictionary database.
In the former method of character recognition, all stroke coordinates must be subjected to the comparison. Thus an enormous amount of information must be processed particularly for characters which vary in stroke order and stroke number. This disadvantageously requires a large capacity of memory for the dictionary database and processing programs and also results in low processing speed.
In the latter method of character recognition, more specifically, the direction of each stroke of a handwritten character is detected with respect to the time at which the user starts to write it (or its originating order) and the detected direction is compared with the dictionary database in memory. The character in the dictionary database that best matches the input handwritten character is determined as a recognized character. While the latter method requires smaller memory capacity for the dictionary database and also provides faster processing speed than the former method, the character recognition rate of the latter method is significantly reduced for a character written in an incorrect stroke order, since the latter method refers to the writing time of the character to detect the writing direction of the character.
Japanese Patent Laying-Open No. 10-154206 discloses a method in which the level of a feature of each stroke's turn in a handwritten character is detected and compared with a dictionary database to identify the character. In accordance with this method the position and angle of each stroke's turn of a character are detected and compared with the dictionary database to identify the character. Thus the amount of information required for character recognition can be reduced and characters written in incorrect stroke orders can also be recognized correctly. However, the character recognition rate of this method is also degraded for cursive characters, since cursive characters have irregular turns caused depending on how the characters are written so that the positions of the turns cannot be detected correctly. This disadvantage is similarly found in the above-mentioned methods of comparing stroke coordinates and comparing writing directions.